This invention relates to apparatus used in liquid vapor contact towers wherein intimate contact between gases and liquids is desired in order to exchange properties or mutually modify conditions of the gases and liquids. More particularly this apparatus relates to directing a liquid downwardly in such a tower in a very uniform distribution pattern at an ultra-slowflowrate.
In industrial processes wherein liquid and vapor are both present in a tower or column, there arises many instances wherein it is desired to add liquid to the process going on inside the tower or to allow vapor to condense to liquid as it rises in the tower and flow downwardly through rising vapor in order to achieve mass or heat transfer between the liquid and gas phases. In other instances liquid containing inhibitors are fed to the tower at predetermined elevations therein in order to prevent or inhibit some undesired event or process from occurring. An example of the purpose of feeding inhibitors is that of feeding inhibitors to prevent polymerization of the reactants and/or products in a tower or packed column. Often such ingibitors is fed with gaseous and liquid substances being re-cycled to the tower.
In any event it is most often desired to have this liquid feed as intimately dispersed in the gas or vapor as possible in order to achieve the homogeneity of the gas-liquid mixture which is required for tight control of the process proceeding in the tower.
To help achieve more uniform mixing of the vapor and liquid phases in the tower, column packing is often used therein.
Further to obtain better mixing in the column packing the liquid fed to it from above is often fed first through mechanical apparatus called distributors. These distributors attempt by various means to separate the liquid being fed downwardly into smaller, spread-apart streamlets which have a substantially uniform pattern of separation between them. It is desired to have these streamlets flow at substantially the same flowrates.
In the past much effort has been devoted to increasing the efficiency of such liquid distributors. See for example U.S. Pat. Nos. 3,446,489; 3,360,246; 3,937,769; 3,273,872; 3,143,581; 3,612,494; 3,916,021; 3,392,967; 3,259,380; 3,006,623; and British Pat. No. 1,364,649. Also see the following commercial catalogs: (1) "Tower Packing and Internals", Bulletin Number 217-Second Edition, pages 10-20, published by Glitsch, Inc. of Dallas, Texas, with copyright date of 1975 A.D.; and (2) "Packed Tower Internals", Bulletin TA-80R, pages 3.0-5.1, published by Norton Company of Akron, Ohio, with copyright date of 1976. Further art in this field is found in the presently pending patent application entitled "Liquid Distributor Apparatus and Method for a Liquid Vapor Contact Column" having U.S. Ser. No. 298,058 and U.S. Filing Date of Aug. 31, 1981, and having Stephen Mark Harper as a common inventor of its invention and the present invention.
Much of the efforts represented by much of the information and equipment disclosed in these publications are directed toward improving liquid distribution in liquid-vapor contact towers. Yet achieving and maintaining uniform liquid distribution still remains a nagging capricious problem in industrial application. Especially is this true when dealing with ultra low liquid distribution flowrates such as liquid flowrates below about 0.8-1.0 gallons per minute per square foot of tower as measured along the square footage of an imaginary horizontal planar section cutting a vertical tower just below the distributor in the tower. One of the constant problems plaguing these distributors is the plugging of their small liquid distribution outlets by debris contained in the liquid. Of course, as outlets start to plug, the flowrates from the remaining open outlets change with liquid maldistribution being the necessary consequence. Another factor contributing to liquid maldistribution is the presence of a vapor or gas phase in the liquid phase. Yet another known problem often encountered in plate-type or trough-type distributors is the imperfect horizontal alignment incurred initially or subsequently by tower shifting on its foundation.
It would be advantageous to have distributors which were much less troubled with maldistribution caused by debris in the liquid, vapor in the liquid and very low flowrates. These and other advantages are achieved by the present invention.